News and views from Diamond Environmental Ltd.

Liverpool

Last week The British Occupational Hygiene Society held a joint conference with the Occupational Hygiene Society of Ireland (OHSI) in Liverpool. Exposure Control and Containment 2 (ECCII), was a follow up to the successful event held in Cork two years ago. The Conference was held in the Crowne Plaza Hotel on the waterfront, just a short distance from the “Three Graces” at the Pierhead.

During the afternoon of the first day of the conference delegates were given the opportunity of joining a site visit. This entailed a short walk to this building, located in George’s Dock, just behind the Mersey Docks and Harbour building.

A large Art Deco style structure faced with Portland limestone and decorated with Egyptian motifs that were popular in the 1930’s, not long after the discovery of the tomb of Tutankhamen. It’s effectively a huge chimney surrounded by offices built as part of the ventilation system for the Queensway Tunnel (also known as the Birkenhead Tunnel). It’s certainly one of the fanciest chimneys I’ve ever seen!

It was designed by Liverpool architect Herbert James Rowse (1887-1963) and the carved Egyptian style decorations on the portals are by sculptor Edmund Charles Thompson (1898-1961).

The control centre for the tunnel ventilation system, as well as one of the ventilation stations, is located here and this is what we went to visit.

The tunnel was opened in July 1934, and at the time, at 3.24 kilometres (2.01 mi) long. it was the longest road tunnel in the world, a title it held for 14 years until the opening of the Vielha Tunnel in Spain in 1948. It remained the longest underwater tunnel though, until 1955. The entrance is right in the centre of Liverpool and being built in the 1930’s it only has a single carriageway of four lanes, two in each direction.

Mersey Travel, who own the tunnel, organise regular tours of the tunnel showcasing its history and allowing the public to gain access to the old control room, ventilation equipment and the tunnel itself. They also can arrange special tours for schools, companies and other organisations. Given the theme of the conference – about the control of exposure to hazardous substances – the tour was customised to highlight how the air quality is controlled.

After donning our hi-viz vests and safety helmets, our guides, Alison and Billy, gave us a potted history of the tunnel and described how it was constructed. Billy was a real “Scouser” – born and bred in Anfield (although a true Evertonian!) with lots of stories and plenty of jokes and wisecracks. A true entertainer!

The tunnel cost £8million to build and employed 1700 men in difficult working conditions under the river bed. 1,200,000 tons of rock and gravel had to be excavated by two teams working from either side of the river. Pilot tunnels were excavated, one starting in Liverpool and the other in Birkenhead, eventually to meet in the centre – less than an inch out of alignment! – on 3 April 1928. The pilot tunnels were then enlarged to create the full sized tunnel. There’s more information about its construction on the Merseyside Maritime Museum Website and a more detailed description here.

First stop was the old control room, which was in use until relatively recently. This required climbing several flights of steps (you need to be fit for this visit!!)

Ventilation of the tunnel to remove contaminants from vehicle exhausts, is provided by massive fans located at 6 ventilation stations, including the one at George’s Dock. Fresh air, brought in from above street level, is blown through the ducts beneath the roadway. The air enters the upper half of the tunnel through outlets18 inches apart at roadway level. The air flow is balanced by varying the size of the outlets to ensure an even distribution of air throughout the tunnel. Contaminated air is extracted through vents in the roof of the tunnel to the exhaust chambers at each of the six ventilating stations.

It’s incredible to think that the original fans, built and installed in the 1930’s, are still in use. They are enormous, with the largest capable of moving 641,000 cubic feet per minute (315 cubic metres per second).

I was rather pleased to hear that one of the two fan suppliers was Walker Brothers of Wigan (my home town) who specialised in equipment for mines. In the 1930’s there was little knowledge or experience of how to control air quality in road tunnels so, perhaps not surprisingly, they fell back on the technology used to ventilate coal mines.

Here’s some old pictures showing the fans being installed.

This diagram illustrates the operation of the ventilation system (showing the Birkenhead side). It appeared in the second edition of a short lived British magazine “Wonders of World Engineering”, published in March 1937.

We were then taken all the way back down and below ground level to look inside the tunnel itself. It’s very narrow and the cars speeded past only centimetres from where we stood on the observation platform. No photographs were allowed to minimise the distraction of drivers of the vehicles passing through the tunnel – we didn’t want to be the cause of an accident.

Then it was back up the stairs to the ground floor where we handed in our safety gear at the end of what was a very informative and entertaining visit.